A clearly emotional Amanda Knox said in an exclusive interview with "Good Morning America" this morning that she "couldn't believe what I was hearing" as she watched the Italian court declare her guilty of murder and sentence her to more than 28 years in prison.

"It really hit me like a train," she told GMA anchor Robin Roberts. "I did not expect this to happen. I really expected so much better from the Italian justice system. They found me innocent once before."

Knox's voice quavered and she paused at times as she struggled to maintain her composure.

"I will never go willingly back to the place where … I’m going to fight this to the very end. It’s not right and it’s not fair," she said.

Knox spent four years in an Italian prison after being convicted of murdering her English roommate Meredith Kercher in Perugia, Italy, where they were both students in 2007.

She was freed when an appeals court threw out the conviction in 2011, but Italy's supreme court ordered the case retried and an appeals court found her guilty Thursday. The court sentenced Knox to 28 years and six months in prison.

With a shaky voice, Knox said she has gone through "waves of reaction" and it "only on my way here that I got my first cry." She said she spoke with an Italian priest who she met in prison and has kept in touch with.

"No, this is wrong," she said at one point, "and I'm going to do everything I can to prove it."

"This is an experience that I have to testify to, that really horrible things can happen and you have to stand up for yourself," Knox said.

Roberts asked the Seattle woman if she was ready for extradition if Italy seeks to have her sent back.

"I'm not," Knox said firmly. She added, "I will never go willingly back."

Knox said she has sent a letter to her lawyer that is addressed to the family of Meredith Kercher.

"It's in the mail. Mainly I just want them to know that I really understand that this is incredibly difficult, that they’ve also been on this never ending thing and when the case has been messed up so much, like a verdict is no longer consolation for them," she said.

Knox's former Italian boyfriend and co-defendant Raffaele Sollecito was also found guilty and sentenced to 25 years. He was found early today at a hotel near the Italian border. Police took him from a hotel to a police station about 1 a.m. to stamp his passport in a way that would prevent him from leaving the country.

Sollecito's lawyer told ABC News that he was not trying to flee the country.

"Sollecito was going to his girlfriend’s house in Treviso," the lawyer said.

Knox said today that one of her first reactions after hearing the verdict was, "Oh my God, Raffaele... He is vulnerable and I don't know what I would do if they imprisoned him. It's maddening."